Canine Mystery: How Dogs Became Man's Best Friend

This is SCIENCE FRIDAY, I'm Ira Flatow. We all know the phrase a dog is a man's best friend. But how did they become such loyal companions? Scientists agree that dogs descended from wolves, eventually evolving into the first domesticated animals, but that's where the consensus ends.

Researchers have been using archaeological records and genetic studies to tease out clues about how dogs and humans came to live together, but they seem to tell different stories of how it happened.

Did dogs become domesticated 30,000 years ago, or was it a lot more recent? Did humans adopt wolf puppies into their lives, or was it the other way around? Did wolves simply become more tolerant of us? That's what we'll be talking about this hour. Our number 1-800-989-8255. You can also tweet us @scifri.

Mark Derr is author of the book "How the Dog Became the Dog: From Wolves to Our Best Friends." He joins us from Miami. Welcome to SCIENCE FRIDAY.

MARK DERR: Thank you.

FLATOW: Greger Larson is an evolutionary biologist and research scientist at Durham University in England. He joins us here. Welcome to the program.

GREGER LARSON: Good afternoon.

FLATOW: Let me ask you, first, to talk about dogs and how dogs - what is the controversy here, Mark? Are wolves ancestors to dogs, or are they more closely related?

DERR: I think it's generally agreed at this point in time that the dog is descended from the wolf and no other canid. The question is where and how that occurred, as you said. And that's open to debate. The debate was joined again this week with the publication of a new paper in Nature suggesting that when wolves began to be able to digest carbohydrates, and they - from feeding in the garbage dumps of just pre-agricultural humans, that that transition allowed them to become dogs.

FLATOW: From feeding in garbage dumps?

DERR: From feeding in garbage dumps. That's a popular - one popular theory. It's not one I subscribe to.

FLATOW: Well, what do you subscribe to?

DERR: Well, I like to be a little heretical and say that I think that early humans and wolves got together from the time they first met on the trail of the big game they were hunting, and they like each other in many ways, and so from the beginning of that union, dogs - wolves and humans were together. From some population of wolves, we're not quite sure which, we had some transformations that occurred that gave us a more doglike animal, and the rest is history.

FLATOW: Greger Larson, why would wolves have been drawn to humans in the first place or vice versa? Where are the benefits for both parties here?

LARSON: Well, I think the first question is really, I think you're absolutely right, why the benefits because they're both omnivores and they're both competing for the same game. So they would be highly suspicious of one another, and it would be active competition. In fact, we know that once dogs are domesticated, wolves get eradicated very quickly. In fact, it's a bit of a surprise that there's still wolf populations left because it's such a contentious relationship between humans and wolves, generally speaking.

But - and I tend to agree. I think that wolves and humans, despite this kind of negativity towards one another, there was a similar purpose. There was a shared desire to seek out similar game, and as a result of that I think that we're not quite sure still when it was, but it was certainly the first domesticated animal and that it was almost certainly something to do with hunting and that there was this relationship that built up between human camps on one side and sort of tame wolves on the other side that were able to tolerate the presence of humans and vice versa.

And they kind of partnered up and started hunting together.

FLATOW: Mark, are archaeological records and genetic studies producing conflicting results about when dogs were domesticated? Where is that debate?

DERR: That debate's been raging since about 1997, when Bob Wain(ph) and Carl Vila(ph) published an article suggesting that the dog was derived from the wolf about 135,000 years ago, which is still a date that's out there. It's pretty extreme, but it's still out there. And at that time, of course, there was no archaeological evidence for such a date, still isn't, and so the archaeologists came back and said show us the bodies, as it were.

And the geneticists have been looking for them ever since. There are some - there are some old remains of doglike animals that go back to about 30,000 years. They're disputed as to whether they're early dogs or not.

FLATOW: But you both would agree that the dog domestication took place before the advent of agriculture and this paper sort of intimating that was the reason?

DERR: I think so.

LARSON: Yeah, that's beyond dispute. I mean, there's only two things about dogs that are not contentious, and one is that it's the very first domesticated animal or plant without question, and that it took place at least a couple thousand years before agriculture, if not much before then.

DERR: I...

FLATOW: Yeah, I'm sorry...

DERR: No, I agree to that, yes.

FLATOW: Tell us, if all dogs descended from wolves, how did we go from that to the hundreds, you know, of very different species? If you look at the dog shows, you look at people having all these dogs, they range from the tiny Chihuahua to the big Rottweilers and such.

LARSON: Most of that change is just within the last 150 years. We have - what we've done to dogs, I mean there was quite a few varieties out, but nobody was really doing breeding with closed breeding lines up until the Victorians. And in fact the first small pet dog was really only in Roman times, about 2,000 years ago.

So - and before that we had a good 10,000 years of domestication. I mean, dogs were always serving a purpose. They always had a job to do. And as soon as that job was fulfilled, or as soon as it was no longer required, then those dogs were eliminated right away. And it's only really in the last 150 years that we've gone absolutely mad with more of an aesthetic idea of what a dog should be, and so they all have to have spots, or they all have to have legs that are this long or all have to have a withers height of 35 inches of whatever it is.

And all of that has been a very recent, very directed, very intentional selection that's generated a massive amount of diversity on what is effectively a very limited genetic template. And so it's like a handful of genes that are affecting all of these things, but dogs by and large are very, very closely related to each other, much more than you would guess, given their morphological disparity.

FLATOW: Was this sort of a commercial thing, people saying, you know, trying to sell dogs to people?

DERR: Initially I think it was not commercial, it was a hobby of the wealthy people. The emerging middle class wanted to prove that they could show their wealth off. (Unintelligible) called it conspicuous consumption and referred often to little dogs like Pekingese. There was a time early in the 20th century when a purebred dog cost more than a Model T Ford.

FLATOW: No kidding. Wow. Let's go to...

DERR: Really the democratization of the breed clubs and kennel clubs really occurred after World War II.

FLATOW: Did you want to jump in there, Greg?

LARSON: Well, I was just going to say that you can - I mean, you can still spend 100,000 or 150,000 dollars on a dog. I mean dogs are getting enormously popular in China now, which is somewhat ironic given that during the Cultural Revolution dogs were virtually eliminated from the entirety of the country, and it was very difficult to find any pet dogs.

And now it's becoming much more of a cultural thing, and so to have a nice big dog, a big hairy dog, a very purebred dog, is something that's becoming a (unintelligible) thing to do, a very chi-chi thing to do. And as a result, the market has gone through the roof and people are spending up to 100,000, 200,000 for a puppy.

FLATOW: No kidding.

DERR: Yes, and the problem is they're often buying Western breeds. They're not - they're ignoring their indigenous dogs.

FLATOW: Interesting, let's go to the...

DERR: What's left of them.

FLATOW: Let's go to the phones. Lynn in Princeton, New Jersey. Hi, Lynn.

LYNN: Hi, I wanted to ask you guys if - well, how and why is it that the way in which dogs came to relate to humans could not be described as a parasitic relationship in that, you know, we - wolves don't take in humans, really, but humans are certainly interested in taking critters in, and they, you know, dogs of course now are, you know, more or less totally dependent, but certainly they got benefits right from the beginning.

FLATOW: Good question, thanks, Lynn.

DERR: Well, there certainly are legends of wolves taking in humans, mostly famously Romulus and Remus and the founding of Rome. But in general you're right. I don't think that dogs are parasitic because they do provide many things. Less so now, but as Greg pointed out earlier, for much of their history dogs have worked. They've earned their keep either as watchdogs...

LARSON: And they still do.

DERR: Yes, indeed.

LARSON: When you consider the range of jobs that dogs are doing now that they never have done before. I mean just think of going through an airport and having bomb-sniffing dogs and cancer-sniffing dogs. And people are putting dogs to uses that they were never used for before.

I mean I think the vast majority of dogs, when we think of them in Western culture, are pet animals that sit at home and sort of make us smile when we get home. But for most of dogs' history, they have been put to very specific tasks, and I wouldn't say it's anything other than very mutualistic.

I mean we've provided them with food and shelter, and they've provided us with a whole range of activities, much more so than any other domestic animal has.

FLATOW: Let me see if I can get a quick call in before the break. Chris in Gillette, Wyoming. Hi, Chris.

CHRIS: How are you doing?

FLATOW: Hi there. Go ahead.

CHRIS: My question is: How do we know, or why do we believe that the wolf came first, and how do we know it wasn't the other way? Maybe the dog went feral, and then the wolf came.

DERR: Well, we do have an example of a population of feral dogs in Australia, the dingo. I think generally there's no evidence that there was a dog existent before the dog. And so in terms of the genetics and what we know from the fossil record, priority goes to the wolf.

FLATOW: Genetically speaking, how close are they, the dog and the wolf?

LARSON: It's difficult to answer that from a - I mean at a percentage figure, but they are - they're much closer to wolves than they are to any other living canid or any other extinct canid as far as we can tell. There is the possibility, I mean, and we know this from a range of different examples, where dogs can reproduce and produce fertile offspring with a number of other things, including coyotes and jackals and red wolves and a variety of other animals.

But - and so there might be some of that DNA kicking around in some of our domestic dogs, but if it's there, it's going to be very, very minute, and the vast majority of everything that is dog is effectively wolf, with a couple of new mutations since domestication that have allowed them to be genetically and morphologically just different enough that we can associate with them in a very different way than we would wolves.

FLATOW: So why are we so afraid to mix in with a wolf, you know, stay away from the wolf, if they're really dogs?

(LAUGHTER)

DERR: Good question. There are people are mixing with wolves...

LARSON: The dog has a very important behavioral difference, which is that - and this has been demonstrated time again, where things like if you point, a dog will follow your finger, but a wolf won't. And so dogs have become humanized in such a way that wolves are still a wild animal that is very much in competition with us for natural resources and are still very wary of us.

So - but a dog and a wolf are very, very different animals. And you wouldn't ever want to treat one like the other.

FLATOW: All right, Mark, we'll get your word in right after the break on that. Our number, 1-800-989-8255, talking about dogs and evolution and their relationship to wolves with Mark Derr, author of the book "How the Dog Became the Dog: From Wolves to Our Best Friends"; Greger Larson, evolutionary biologist, research scientist at Durham University in England. Our number, 1-800-989-8255. You can tweet us @scifri. Stay with us. We'll be right back after this break.

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FLATOW: I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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FLATOW: This is SCIENCE FRIDAY. I'm Ira Flatow. We're talking this hour about dogs and evolution and how they domesticate, were domesticated from wolves. Our number, 1-800-989-8255. Our guests are Mark Derr, author of the book "How the Dog Became the Dog: From Wolves to Our Best Friends"; Greger Larson, evolutionary biologist and research scientist at Durham University in England. As I say again, our number 1-800-989-8255. You can tweet us @scifri.

Mark, did you want to jump in about why, you know, why do they tell us to stay away from wolves if they're so closely related?

DERR: Well, I think the answer is that the wolf is a wild animal, and people want to keep it that way and not mix it in with dogs or vice versa. But the fact is that there are still people who are cross-breeding dogs and wolves. They don't do it to the extent that it's going to make much difference or any difference in the greater dog gene pool, but we also have the problem of the dog being derived from a wolf.

And so I think part of the issue is that when we look at wolves today, we're looking at animals who have been persecuted, often in organized fashion, for well over 1,000 years. And that has to shape their evolution the same way we have shaped the dog.

Yet at the same time there are people who throughout history have tamed wolves or socialized wolves, and even in the 1960s in this country there were people who socialized adult wolves, which was said not to be able to be done.

FLATOW: Let's talk a bit about more - Greg, there was a study done in Russia where they tried to figure out the mechanism that led to the domestication of dogs by looking how to tame foxes. Can you tell us a little bit about that?

LARSON: Sure, this is Dmitry Belyaev, who in the 1950s had this idea that - because for a long period of time, then and as now, people were looking at the dog and trying to figure out exactly how it became domesticated. And a lot of people worked on a trait-by-trait basis. They would say, well, it's got floppy ears, so what evolutionary mechanism can we think about to ensure that the dogs' ears would get floppy?

And people were saying, oh, well, you would select for floppy ears so that it would cover the ears up slightly, and that way it couldn't hear the call of the wild. And what Belyaev was saying was like, look, you have a whole bunch of domestic animals, many of which have a lot of the same kind of general traits.

You get really - you get piebald coats, and you get smaller overall size, you get scrunched faces, upturned tails, floppy ears. And you don't just see this in dogs. You see it in cows and pigs and sheep and goats and all kinds of stuff. And what he figured was rather than selecting for an individual trait, that all, this whole suite of characteristics came along as hitchhiking on what he thought would just be a behavioral trait.

And in order to demonstrate this, he got a bunch of silver foxes, which had never been domesticated before, and he put them in cages, and he did a very simple experiment. He put his hand into the cage, and he measured whether or not they would either cower into the back of the cage and show a fear response, whether they'd be aggressive and try and bite your hand or whether they would be curious and come up and smell the hand of the person who had put their hand in.

And so as a result, he then took those - the top 10 percent of the most curious ones and bred them and kept doing 10 percent, 10 percent for every single subsequent generation, and after only about 20 or 30 years - or he was seeing lots of changes in that time - but after 20 or 30 years, what he developed was a tamed fox.

And by selecting solely for a behavioral trait, what he got was tame foxes that were curious and barked and had floppy ears and piebald coats and upturned tails and all kinds of other stuff. So - and demonstrating his point was that all you had to do was get tameness as a selection pressure, and the whole rest of these physical morphological traits would just kind of tow along and result in a population that was very, very different from the founder population, even though you never selected for any of those traits individually.

And so what people have been suggesting as a result of that is that dog domestication probably occurred along something of the same kinds of lines, where rather than just simply going out and purposefully grabbing a puppy or trying to get a population of wolves and seeing one black one and then going out and grabbing that and trying to select for that, that it was more of a very long-term, gradual process where there was a social and behavioral alteration where the dog, or the wolves, that were most tame already then were getting closer to the humans camps and started eating the things that the human camps had, a lot of the waste products. And those that were able to do so set themselves along this path toward eventual kind of full dogs that we have now.

But those initial processes were not being generated by humans, not being led by humans. And it was just kind of a closening of the relationship and a little bit more of a tameness between both the humans and the dogs.

DERR: Yes, I call them stump-diving, self-domesticated dogs.

LARSON: That seems appropriate.

DERR: The problem with that is that it removes the human from the equation, I think, and we look at how dynamic the human-dog relationship is now and has been, and it's hard to believe that - for me to believe that it would be such a passive experience on the part of early humans.

FLATOW: Uh-huh.

LARSON: Well, I think very initially, I mean, it's certainly passive to start because you can't - there's no way the people without any other domestic model would look at a wolf, who they are competing with for resources, and say. you know what? I'll bet if we spend 15 generations selecting for tameness that we can get a puppy out of that that's really going to be cute.

It's just - you can't start with the final product and then assume that there was a nice, easy, direct path to go from a wolf to a dog. Now absolutely, I mean, humans were smart, and they could do a lot of things deliberately, but I think the initial processes that got things underway didn't have anything to do with any kind of deliberate action on the part of humans who had some sort of forethought or idea of what they wanted to get out of this relationship.

FLATOW: All right...

DERR: No, I don't think they were - they had that kind of forethought, nor do I think cuteness was the goal. But I do think that - wolves, we know - people feed animals all the time, and there are ways that wolves could have helped humans hunt without even being in competition with them. For instance, the humans could follow the wolves to the game they were looking for an interrupt and steal the kill from the wolf. That certainly happens now. People follow wolves, or they follow ravens that are following wolves to caribou herds in the Arctic.

And so I think you have to look from the beginning at an active relationship. That's not to say there's not some self-selection involved by the wolves. Certainly there has to be.

FLATOW: Gentlemen, thank you, we've run out of time. And quite fascinating. My guests are Mark Derr, author of the book "How the Dog Became the Dog: From Wolves to Our Best Friends." Greger Larson is an evolutionary biologist and research scientist at Durham University in England. Thank you, gentlemen, for joining us today.